Since we do not have permission to copy the actual rebuild procedure, the following links are to another website and illustrate rebuilding the CVK40 carburetor; however, this info also applies to the CVK30 installed on the Ninja 250. You will need to refer to other links in the DIY stickies (above) for removal of the carburetors, etc.
After going to the following link, you can click on each pic and enlarge same for more detail. Just ignore the references to the KLR650 bike. Of course, there is a lot more info available on this website that maybe of interest to all.
http://www.multisurfacemotorcycling....arb/carb05.htm